(1) Field of the Invention
The present invention relates to an ink composition for a writing board. More particularly, it relates to an ink composition for a writing board, which has such a property that characters or marks written on a writing board incapable of absorbing the ink therein can be easily erased by lightly wiping the writing board with a cloth or paper.
(2) Description of the Related Art
A conventional wipe-erasable ink for a writing board is a dispersion or solution of a colorant such as a pigment or dye, a resin binder and an additive for manifesting erasability in an organic solvent. When a pigment is used, the ink is little absorbed on the writing board and the erasability is good. However, the dispersibility of the pigment tends to be non-uniform, the stability of the dispersion is poor, and the flowability of the ink through the pen-tip decreases during storage and the writing becomes faint. Namely, the ink has a poor long-period stability. When a dye is used, the stability during the storage is satisfactory, but if writing is allowed to stand for a long time without wiping, the ink is absorbed on the writing board and it is difficult to completely erase the writing by wiping.